1. Technical Field Pertinent to the Invention
The present invention relates to a laser power control method and an optical disc recording apparatus, which is are used for performing data recording on an optical disc such as a CD-R (Compact Disc-Recordable) disc and a CD-RW (Compact Disc-ReWritable) disc, and a structure of a record layer of the optical disc.
2. Prior Art
There are provided various kinds of optical disc recording apparatuses used for performing data recording on an optical disc such as a CD-R and a CD-RW. As a data recording mode, there are a CAV (Constant Angular Velocity) mode which performs driving of the disc with fixing a number of revolutions of the disc (namely, fixing the angular velocity) and a CLV (Constant Linear Velocity) mode which carries out driving of the disc with fixing a linear velocity of a track formed on the disc.
Of these modes, the CAV mode has been widely adopted for performing recording at a higher velocity since a number of revolutions of the disc is fixed, and there is no need to effect the complicated rotation drive control. In the CAV mode, however, a number of revolutions of the disc is fixed and, on the other hand, a trace length by a laser spot (which is proportional to the recording linear velocity) varies depending on a radial position of the spot on the disc. For example, when a recording linear velocity at the innermost periphery of the disc is set to a quadruple velocity of a standard velocity, a recording linear velocity at the outermost periphery of the disc reaches a decuple velocity of the standard velocity. Further, when the recording linear velocity at the innermost periphery of the disc is set to an octuple velocity, it reaches a twentyfold velocity on the outermost periphery of the disc.
As described above, in the optical disc recording apparatus adopting the CAV mode, the recording linear velocity increases as a radial recording position moves from the inner peripheral side toward the outer peripheral side. In diagram of this, the recording laser power is controlled to change in accordance with a radial recording position such that deterioration of a recording quality caused by the variation in the recording linear velocity is suppressed in the conventional optical disc recording apparatus adopting the CAV mode.
However, even if the recording power value is changed in accordance with the recording position, i.e., in matching with the recording linear velocity, there still occurs a problem of lowering of the recording quality. Furthermore, with the recent speeding up of recording, a difference in the recording linear velocity between the innermost peripheral position and the outermost peripheral position increases in the CAV mode, and the above-described deterioration of the recording quality may possibly become more prominent.